Limit-switch for electric motors.



, H0. 838,681. PATENTED DEC. 18, 1906.

S. BURROWES.

LIMIT SWITCH FOR ELECTRIC MOTORS.

APPLICATION FILED FEB. 19, 190B.

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Specification of Letters Patent.

Patented Dec. 18, 1906.

Application filed February 19, 1906. Serial No. 301,799.

To It whom it may concern:

Be it known that I, SIDNEY BURROWES, of Falls View, in the Province of Ontario, Canada, have invented certain new and useful Improvements in Limit-Switches for Electric Motors, of which the following is a specifica- 131011.

My object is to devise a switch which will out 01f the current from a motor after the latter has made a predetermined number of revolutions; and my invention consists, essentially, of a screw revolved by the motor and operating a nut, which by traveling along the screw sets in operation mechanism for operating a switch controlling the current supplying the motor, substantially as hereinafter more specifically described, and then definitely claimed.

Figure 1 is aside elevation, partly in section, of my device. Fig. 2 is an end elevation, partly in section, of the same. Fig. 3 1s a plan view of the same.

In the drawings like letters of reference indicate corresponding parts in the different figures.

A is the frame of the apparatus, suitably shaped to support the different parts. On this frame is journaled the screw B. The end O of this screw may be driven in any suit able manner from the shaft of the motor the switch is designed to control. On this screw travels the nut D, ofsome considerable length, as shown. This nut is held from turning by two parallel guides E, which engage opposite sides of the nut. (See particularly Fig. 2.)

Slidably supported upon the nut is the motion-piece F. This motion-piece is provided at opposite sides with pins G, which project through suitable slots in the guides E. With these pins engage the slotted upper ends of the fork-lever H, pivoted on the frame of the apparatus at a. The lower end of this lever H is slotted, as shown, to engage a suitable pin or bar 1, formed at the upper end of the switch-lever J. This switch-lever is provided with switch-blades K. These switch-blades K are adapted to engage the spring contacts L.

Any number of switch-blades and contactpieces may be employed, depending on the work that the switch is intended to do. In the drawings I show three pairs of switchblades and three pairs of springcontact pieces.

I propose to use the device with an arrangement of wiring whereby after the switch has been moved the contacts are left in position for the running of the motor in the reverse direction and whereby a brake may be operated to assist in stopping the motor after the current has been cut off; but this arrangement forms no part of the present invention and is merely mentioned to indicate the purpose to which the invention may be applied.

The motion-piece Fis normally maintained in a central position by means of the coil springs M, which engage opposite sides of the contact-piece. and the opposite ends of the nut. At each side of the central point is a detent N, pivoted on the frame of the machine, each detent being provided with a beveled end whereby the motion-piece is enabled to raise the end and pass into engagement with the detent. Each detent is maintained in its normal position by means of a coil-spring O, connected with the detent and with the post P, formed on or secured to the frame of the machine. Stops Z), secured to the frame of the machine, serve to limit the downward movement of the detents. Each detent below this pivot has a shoulder Q formed thereon. Each end of the nut is provided with a part adapted to engage the shoulder of the adjacent detent. These parts are preferably formed of set-screws R, screwed through the end of the nut, so that the contacts are thus adjustable.

The operation of the device is substantially as follows: The screw A is revolved onehalf of the number of turns it is desired the motor shall make before the switch operates. It will then be found that the motion-piece F has been moved to a position enabling it to engage with one of the detents N. The screw is then connected to the motor and the screw caused to rotate in the reverse direction. As soon as the screw has traveled far enough to bring the forwardlytraveling setscrew B into contact with the adjacent detent with which the motion-piece is engaged the detent will be lifted and the motion-piece re leased but as the spring back of the motionpiece has been compressed by the travel of the nut the motion-piece will be shot forward into engagement with the other detent N. This reverses the position of the switch. This reversal of the position of the switch may be caused simply to stop the motor or to leave connections in position for the reversal of the motor when the latter is'again started and also to apply a brake, if desirable.

It will be seen that my limit-switch is ab solutely certain in its operation and will operate the switch after the motor has made a given number of revolutions in either direction. The device is also exceedingly simple and not liable to derangement.

What I claim as my invention is 1. A limit-switch comprising a j ournaled screw; a nut on the screw suitably held from revolving without interfering with its longitudinal movement on the screw; a switch in an electric circuit; a motion-piece adapted to operate the switch; a detent adapted to hold the motion-piece in one position; means tending to move the motion-piece from said position; and a part on the nut adapted to engage the detent to release the motionpiece, substantially as described.

2. A limit-switch comprising a journaled screw: a nut on the screw suitably held from revolving without interfering with its longi tudinal movement 011 the screw: a switch in an electric circuit: a motion-piece adapted to operate the switch; means tending to maintain the motion-piece in a central position: a detent at each side of the central position, each adapted to engage and hold the motionpiece; and parts on the nut, each adapted to engage one of the detents to release the motion-piece, substantially as described.

3. A limit-switch comprising a journaled screw; a nut on the screw suitably held from revolving without interfering with its longitudinal movement on the screw; a switch in an electric circuit; a moti0n-piecelongitudinally movable on the nut; means controlled by the motion-piece for operating the switch; adetent adapted to hold the motion-piece in the position it occupies when the switch is closed; a spring adapted to move the motionpiece to open the switch; and a part on the nut adapted to engage the detent to release the motion-piece, substantially as described. 4. A limit-switch comprising a journaled screw; a nut on the screw suitably held from revolving without interfering with its longitudinal movement on the screw; a switch in an electric circuit; a motion-piece longitudinally movable on the nut; means controlled by the motion-piece for operating the switch; springs engaging the nut and the motionpiece normally tending to maintain the latter in a central position; a detent at each side of the central position, each adapted to engage and hold the motion-piece; and parts on the nut, each adapted to engage one of the detents to release the motion-piece, substan tially as described.

Falls View, Ontario, February 14, 1906. SIDNEY BURROWES. In presence of- IDA M. GALLINGER, ETHEL CoULsoN. 

